This invention relates to a rotary phase separator for separating liquid from gas in a zero or variable gravity environment.
Typically, the separation of gas from a liquid is accomplished by allowing entrapped gas to bubble upward out of the liquid under the influence of gravity. This method does not work in zero or variable gravity environment encountered by space vehicles. Typically, in such environments, a liquid/gas circulation system is used that includes a circulating pump; an accumulator to accommodate volume changes in the liquid/gas mixture and a separator to separate the liquid phase from the gas phase. Such systems are utilized to generate oxygen by electrolysis of water.
Current state of the art systems utilize bellows accumulators to accommodate volume changes due to variation in the amount of oxygen being delivered and a special membrane separator to remove generated gas from the liquid stream. When used in a zero gravity environment, a bellows accumulator can become gas bound, leading to reduced liquid capacity in the accumulator. The membrane separator must be replaced often because the membrane becomes contaminated.
To eliminate the need for a membrane separator, a rotary phase separator that uses centrifugal force to separate the liquid phase from the gas phase can be utilized. However, a typical rotary phase separator requires a liquid control system that vents accumulated gas as necessary to maintain a relatively constant liquid level. Further, in such systems it is of critical importance that the separated phases not be mixed upon exit of the separator such as may occur on start up before sufficient rotational speed has been attained to sufficiently separate the phases of the mixture.
For this reason it is desirable to develop a system that does not become contaminated during use, which does not require periodic replacement and which can accommodate liquid level fluctuations, thereby acting as an accumulator.
The invention is a rotary phase separator assembly including an accumulator and a liquid outlet valve for use in a closed loop recirculating system to separate the phases of a liquid/gas mixture at varying liquid levels.
The rotary phase separator has a separating chamber capable of accommodating different liquid levels and thereby acts as an accumulator for a closed loop gas/liquid-recirculating system. The rotary phase separator assembly includes an accumulator/separator chamber defined by an inlet housing and an outlet housing. The accumulator/separator chamber is cylindrically shaped about a longitudinal axis. An inlet port for the liquid/gas mixture opens tangentially into the accumulator/separator chamber such that incoming flow of the mixture initiates a spinning motion. The inlet port opens into a pre-swirl chamber that begins the separation of the liquid from the gas.
The liquid and gas continue to rotate about the axis and are driven by a plurality of disks and cylinders attached to a hollow shaft driven by a motor. Hydrodynamic bearings are provided to support the shaft such that the shaft will rotate on a cushion of liquid drawn from the accumulator/separator chamber. The hydrodynamic bearings substantially eliminate any mechanical friction to increase the reliability and life of the entire assembly. The disks and cylinders are in frictional contact with the liquid/gas mixture to create a centrifugal force that throws the liquid toward the outer diameter of the accumulator chamber. As the liquid is thrown to the outside of the accumulator chamber, the gas is displaced and migrates toward the axis about the hollow shaft.
The disks include a plurality of holes disposed near the axis to allow gas to flow through the disks along the shaft to an opening within the shaft leading to the hollow portion of the shaft. Gas within the hollow section of the shaft exits through a non-rotating gas outlet tube to a gas outlet port. The gas outlet tube includes a valve member actuated by a solenoid to seal the gas outlet tube shut when the shaft is not rotating and until sufficient gas has accumulated within the accumulator/separator chamber to facilitate phase separation.
The valve is required to prevent liquid from exiting through the gas outlet port. The inner walls of the hollow section of the shaft are tapered toward the opening in the shaft. With the shaft spinning, centrifugal force drives any liquid trapped within the hollow section along the tapered walls of the shaft and through to the opening to reenter the accumulator/separator chamber.
Liquid rotating along the outer diameter of the accumulator/separator chamber exits through a liquid outlet valve. The liquid outlet valve includes a valve seal biased closed against inner and outer seats by a plurality of control springs equally positioned about the outer diameter of the accumulator/separator chamber. The control springs exert sufficient load on the valve seal to remain closed until a predetermined pressure differential is reached between liquid in the liquid outlet and liquid in the accumulator/separator chamber. Control of the liquid outlet is required to prevent gas from exiting along with the liquid through the liquid outlet during system start up.
The subject invention includes an accumulator chamber to accommodate varying levels of liquid such that a separate liquid control system is not required, and gas and liquid outlet control valves that remain closed until the rotary phase separator attains optimal separation conditions to prevent mixing of phases between the liquid and gas outlet ports.